1. Field of the Disclosure
The present disclosure relates to benzothiazole compounds as anti-tubercular chemotherapeutic agents and the process for the preparation thereof. Particularly, the present disclosure relates to 2,6-substituted benzothiazole compounds of general “formula A”.
    X=—N═CH—, —NH—CO—, —CO—    Ar=Phenyl, 4-methylphenyl, 4-methoxyphenyl, 4-trifluoromethylphenyl, 4-trifluoromethoxyphenyl, 4-fluorophenyl, 4-chlorophenyl, 2-chloro-3-methoxyphenyl, 3,5-dimethoxyphenyl, 3,4,5-trimethoxyphenyl, pyridyl, nicotenyl, isonicotinyl, 5-nitro-2-furyl, styryl, 4-fluorostyryl, 4-methylstyryl, 4-methoxystyryl, 4-trifluorostyryl, 4-trifluoromethoxystyryl, 5-nitro-2-furyl, 1-methyl-4-nitro-1H-2-pyrrolyl, 1-methyl-5-nitro-1H-2-imadazolyl, 1-methyl-3-nitro-1H-2-pyrazolyl    R=Hydro, Methyl, Methoxy, Trifluoromethyl, Trifluoromethoxy, Fluoro, Chloro, Nitro, 5-Nitrofuran-2-carboxamide, 5-Nitrothiophene-2-carboxamide, 1-methyl-4-nitro-1H-2-pyrrolcarboxamide, 1-methyl-5-nitro-1H-2-imadazolcarboxamide, 1-methyl-3-nitro-1H-2-pyrazolcarboxamide
The structural formula of these benzothiazole compounds is given below and is represented by the following compounds of formula 3a-p, 4a-h, 6a-w and 8a-d.
    R=H, CH3, OCH3, CF3, OCF3, F, Cl, NO2     X=O, S
    R=H, CH3, OCH3, CF3, OCF3, F, Cl, NO2
    Ar=Phenyl, 4-methylphenyl, 4-methoxyphenyl, 4-trifluoromethylphenyl, 4-trifluoromethoxyphenyl, 4-fluorophenyl, 4-chlorophenyl, 2-chloro-3-methoxyphenyl, 3,5-dimethoxyphenyl, 3,4,5-trimethoxyphenyl, pyridyl, nicotenyl, isonicotinyl, 5-nitro-2-furyl, styryl, 4-fluorostyryl, 4-methylstyryl, 4-methoxystyryl, 4-trifluorostyryl, 4-trifluoromethoxystyryl
    Ar=5-nitro-2-furyl, 1-methyl-4-nitro-1H-2-pyrrolyl, 1-methyl-5-nitro-1H-2-imadazolyl, 1-methyl-3-nitro-1H-2-pyrazolyl
2. Discussion of the Background Art
As a part of investigation of new chemotherapeutic agents from this laboratory, over the past eight years our research efforts have been focused towards the intervention of new scaffolds with good antimycobacterial activity and eventually to develop new anti-tubercular agents that can improve the current therapeutic regimen as well as effective in the treatment of MDR-TB (Kamal, A.; Babu, A. H.; Ramana, A. V.; Sinha, R.; Yadav, J. S.; Arora, S. K. Bioorg. Med. Chem. Lett. 2005, 15, 1923-1926; Kamal, A.; Reddy, K. S.; Ahmed, S. K.; Khan, M. N. A.; Sinha, R. K.; Yadav, J. S.; Arora, S. K. Bioorg. Med. Chem. 2006, 14, 650-658; Kamal, A.; Ahmed, S. K.; Reddy, K. S.; Khan, M. N. A.; Shetti, R. V. C. R. N. C.; Siddhardha, B.; Murthy, U. S. N.; Khan, I. A.; Kumar, M.; Sharma, S.; Ram, A. B. Bioorg. Med. Chem. Lett. 2007, 17, 5419-5422).
In early 80s, diverse biological properties have been reported on benzothiazole scaffold including anti-tubercular activity by different research groups around the globe. (Palmer, P. J.; Trigg, R. B.; Warrington, J. V. J. Med. Chem. 1971, 14, 248; Katz. L.; J. Med. Chem. 1953, 75, 712; Palmer, P. J.; Ward, R. J.; Miyamastu, H.; Uneo, H.; Shimizu, H.; Hosono, J.; Tomari, M.; Seida, K.; Suzuki, T.; Wada, J. J. Med. Chem. 1974, 17, 491; Shi, D-. F.; Bradshaw, T. D.; Chua, M-. S.; Westwell, A. D.; Stevens M. F. G. Bioorg. Med. Chem. Lett. 2001, 11, 1093.
Klimesova and co-workers have developed the bezylsulfanyl moiety at C-2 position of benzothiazole with good antimycobacterial activity. Further, Schiff bases and hydrazones of benzothiazoles are also found to be active against Mycobacterium tuberculosis (Koci, J.; Klimesova, V.; Waisser, K.; Kaustova, J.; Dahsec, H.-M.; Mollmannc, U. Bioor. Med. Chem. Lett. 2002, 12, 3275; Katz. L.; J. Am. Chem. Soc. 1953, 75, 712). Recently Kozikowski and co-workers have developed the 2-methyl-5-amido benzothiazoles as potential anti-tubercular agents (Huang, Q.; Mao, J.; Wan, B.; Wang, Y.; Brim, R.; Franzblau, S. G.; Kozikowski, A. P.; J. Med. Chem. 2009, 52, 6757). These molecules are believed to inhibit the HisG enzyme of Mycobacterium tuberculosis (Cho, Y.; Ioerger, T. R.; Sacchettini, J. C. J. Med. Chem. 2008, 51, 5984). In addition nitrobenzothiazole amides have shown interesting anti-tubercular activity, by binding to HisG enzyme of M. tb (de Carvalho, L. P. S.; Lin, G.; Jiang, X.; Nathan, C. J. Med. Chem. 2009, 52, 5789; Dykhuizen, E. C.; May, J. F.; Tongpenyai, A.; Kiessling, L. L. J. Am. Chem. Soc. 2008, 130, 6706).
On the other hand, nitrofuran is an important scaffold in many potential anti-tubercular agents Lee, R. E., Tangapally, R. P., Yendapally, R., McNeil, M., Lenaerts, A. US 2005/0222408 A1; Tangallapally, R. P., Yendapally, R., Lee, R. E., Lenaerts, A. J. M., Lee, R. E., J. Med. Chem. 2005, 48, 8261.
Similarly, 5-nitrothiophene key intermediate in many active anti-tuberculosis compounds (Rando, D. G.; Sato, D. N.; Siqerira, L.; Malvezzi, A.; Leite, C. Q. F.; Amaral, A. T.; Ferreiraa, E. I.; Tavaresa, L. C.; Bioorg. Med. Chem. 2002, 10, 557; Murugasu-Oei, B.; Dick, T. J. Antimicrob. Chemother. 2000, 46, 917). These findings have encouraged us for the design and synthesis of new nitrofuran/nitrothiophene conjugated benzothiazoles and subsequently evaluated for activity against tubercular cultures.
The main object of the disclosure is to provide the new benzothiazole compounds as useful anti-tubercular chemotherapeutics.
Another object of the present disclosure is to provide a process for the synthesis of these new benzothiazole compounds as useful chemotherapeutic agent against sensitive and MDR-strains of TB.
Another object of the present disclosure is to provide a new mechanistic anti-tubercular agents against sensitive and MDR strains of tubercle bacilli.
Another object of the present disclosure is to provide new compounds based on the benzothiazole scaffold in good yields.